The present invention relates to systems and apparatus for managing gas flow through internal combustion engines; more particularly, to one or more valving devices associated with the intake manifold of an internal combustion engine; and most particularly, to an intake manifold assembly for an internal combustion engine, such as a diesel engine or a variable valve lift gasoline engine, wherein an exhaust gas recirculation valve, a manifold inlet air control valve, and swirl port control valves are integrated into the assembly and are actuated by a camshaft.
It is a characteristic of diesel engines and some variable valve lift gasoline engines that virtually no vacuum exists in the intake manifolds of such engines. The lack of vacuum creates problems in providing vacuum-assisted functions for applications such as automotive vehicles, marine vessels, and stationary power generators. A conventional gasoline-powered engine includes a throttle valve at the inlet to the intake manifold to control the flow of air into the engine and thereby to regulate the speed of the engine. Such throttling of the inlet variably creates a subatmospheric condition in the manifold. Recirculation of exhaust gas into the intake manifold uses a pressure drop between the exhaust manifold and the intake manifold to draw exhaust gas into the intake manifold. Such a pressure drop is virtually non-existent in an unmodified diesel engine and also in a gasoline engine wherein gas flow is controlled by varying the lift of the intake valves.
It is known to create manifold vacuum in a diesel intake manifold by providing an air control valve at the manifold inlet, typically a rotary butterfly-type valve. Such a valve is typically actuated by an electric motor and gear train or a stepper motor and is provided as a subassembly which must be attached to the manifold as by bolting and which requires its own power and control connections in a wiring harness. Disadvantageously, a rotary butterfly valve has a highly non-linear flow profile as a function of valve angle; is difficult to close completely without jamming; and typically passes significant air flow in the xe2x80x9cclosedxe2x80x9d position.
It is further known to provide an exhaust gas recirculation (EGR) valve having its own actuator and valve body which also must be bolted to the intake manifold. EGR valves typically are actuated by an electric solenoid in either a position-modulated or time-modulated mode, requiring additional and separate power and control connections. Further, such solenoids are known to be vulnerable to failure from corrosion by permeated exhaust gas. Prior art EGR valves provide exhaust gas globally to the interior of the intake manifold which then distributes the gas along with intake air via runners to the individual cylinders.
It is further known to provide dual intake ports to each diesel cylinder, one such port being open at all times and the other such port being closable by a butterfly-type xe2x80x9cswirlxe2x80x9d valve. The ports are off-axis of the cylinders such that when the swirl valves are closed, as under low engine load conditions, air entering the cylinder is swirled advantageously to center the fuel charge in the cylinder. Typically, the individual swirl valves are actuated by, for example, electrically-powered rotary actuators similar to that known for a throttle valve.
It is a principal object of the present invention to simplify an air intake manifold and associated control valving for a diesel engine to reduce manufacturing cost, ease assembly, improve and integrate air control through an engine, and increase engine reliability.
It is a further object of the invention to mechanically link and actuate such valving, including swirl valves, internally within the air intake manifold.
Briefly described, an integrated intake manifold assembly in accordance with the invention includes a poppet manifold vacuum regulating valve (MVR valve) disposed at the air inlet to the manifold to regulate air flow into the manifold; a poppet EGR valve disposed on the manifold to regulate exhaust gas flow into the air intake system; and a bi-directional camshaft and cams for operating simultaneously the MVR valve and the EGR valve. The valve bodies are integrally formed in the wall of the intake manifold. The camshaft is driven by a single brush DC motor and gear train. The cams are arranged on the shaft to provide optimum synchronized opening and closing of the related valves. The cams may also be individually shaped as needed to optimize the actuation profile of each valve. When used on a diesel engine, the assembly may further include a swirl valve plate disposed between the manifold and the engine head and having a plurality of ganged swirl valves actuated by linkage connected to the camshaft and internal to the manifold and swirl plate. Preferably, the swirl valve plate is also ported as a distribution rail to receive exhaust gas from the EGR valve and distribute it to the individual cylinders, bypassing altogether the interior of the intake manifold and obviating soot deposits in the manifold.
The valve poppets of the MVR and EGR valves are modified as forked yokes which engage the camshaft as reciprocating struts to minimize side loading of the valve stems by the rotary action of the cams.
An integrated intake manifold assembly in accordance with the invention, when compared to prior art assemblies of stand-alone components, eliminates eight bolts and two gaskets; eliminates two actuators and related wiring; eliminates vacuum actuation and hoses; reduces soot in the air intake system, protecting air components; reduces electrical connections to two; simplifies manufacture and assembly; and reduces the overall size and mass of the air control system.